In a prior art matrix type color liquid crystal display, at least part of electrodes for driving liquid crystal are formed on one of a pair of opposed substrates and color filters and black matrixes are formed on the other one of the opposed substrates. In a thin film transistor (TFT) type liquid crystal display, which is a typical liquid crystal display, thin film transistors and a group of interconnection electrodes are formed on one substrate, and color filters and black matrixes are formed on the other substrate.
In such a prior art display in which thin film transistors and color filters are respectively formed on a pair of opposed substrates, when a cell is formed by superimposing the pair of substrates to each other, it is required to accurately align a large number of corresponding pixels to each other. However, as a substrate size becomes larger, there may easily occur offset of pixels between the two substrates due to thermal expansion of the substrates or the like. For this reason, alignment of the pixels must be performed for a long period of time using a high precision aligner, to thereby significantly degrade productivity.
On the other hand, to solve such a problem on alignment of pixels, a technique has been proposed, for example, in Japanese Patent Laid-open Nos. Hei 2-54217 and Hei 2-302727, wherein thin film transistors, a group of interconnection electrodes, color filters, and black matrixes are formed on one substrate. In the technique disclosed in the above documents, however, planar pixel electrodes and a counter electrode are formed on the substrates in such a manner as to hold liquid crystal therebetween. Accordingly, the color filters on the pixel electrodes act as capacitance elements connected in series to the liquid crystal, to thereby significantly reduce a voltage applied to the liquid crystal. In general, liquid crystal has a dielectric constant being as very high as about 10 (average value), while a resin material forming the color filters has a dielectric constant being as low as about 3 to 6. As a result, even if the color filter is formed to a thickness smaller than that of the liquid crystal, it exerts a large effect on a drop in voltage applied to the liquid crystal.
Further, WO91/10936, U.S. Pat. No. 4,345,249, and EPO588562A2 propose a method of applying an electric field to liquid crystal in the direction substantially parallel to a substrate plane (horizontal electric field applying method). In this method, since major axes of liquid crystal molecules are substantially in parallel to the substrate plane and thereby they are not raised, the visibility is not dependent on a viewing angle, that is, the angle of visibility becomes wider. The method disclosed in the above documents fails to examine a reduction in unevenness of luminance, improvement of numerical aperture, and improvement of productivity.
An object of the present invention is to provide a color liquid crystal display having a high productivity.
Another object of the present invention is to provide a color liquid crystal display having no unevenness of luminance.
A further object of the present invention is to provide a color liquid crystal display having a high numeral aperture.